Added/updated snippets for docs (#2318)

docs/doc_examples/e650d73c57ab313e686fec01e3b0c90f.asciidoc

@@ -0,0 +1,21 @@
+// This file is autogenerated, DO NOT EDIT
+// Use `node scripts/generate-docs-examples.js` to generate the docs examples
+
+[source, js]
+----
+const response = await client.reindex({
+  source: {
+    index: "my-index-000001",
+  },
+  dest: {
+    index: "my-new-index-000001",
+    version_type: "external",
+  },
+  script: {
+    source:
+      "if (ctx._source.foo == 'bar') {ctx._version++; ctx._source.remove('foo')}",
+    lang: "painless",
+  },
+});
+console.log(response);
+----